Ink composition

Abstract

An ink composition includes colorant, hydroxylated and non-hydroxylated co-solvents, and water. A weight percent ratio of hydroxylated to non-hydroxylated co-solvents ranges from 46:54 to about 62:38. The composition also includes an acid and a polyurethane copolymer binder. The acid is selected from the group consisting of oleic acid, linoleic acid, undecanoic acid, dodecanoic acid, tridecanoic acid, and combinations thereof. The binder is formed from the polymerization of a diisocyanate and at least three diols including a first diol containing a hydrophilic stabilizing group, and a second diol having less than 8 atoms in a backbone chain between two hydroxyl groups. A mole percentage of the second diol is at least 30% of a total mole percentage of diol monomers in the binder. An acid number of the binder ranges from 50 to 75. The composition also includes lithium present in an amount ranging from about 50 to about 400 ppm.

What is claimed is: 
     
       1. An ink composition, comprising:
 a colorant; 
 a hydroxylated co-solvent; 
 a non-hydroxylated co-solvent, wherein a weight percent ratio of the hydroxylated co-solvent to the non-hydroxylated co-solvent in the ink composition ranges from 46:54 to about 62:38; 
 an acid selected from the group consisting of oleic acid, linoleic acid, undecanoic acid, dodecanoic acid, tridecanoic acid, and combinations thereof; 
 a polyurethane copolymer binder formed from the polymerization of a diisocyanate and at least three diols including a first diol containing a hydrophilic stabilizing group, and a second diol having less than 8 atoms in a backbone chain between two hydroxyl groups, wherein a mole percentage of the second diol is at least 30% of a total mole percentage of diol monomers in the polyurethane copolymer binder, and wherein an acid number of the polyurethane copolymer binder ranges from 50 to 75; 
 lithium present in an amount ranging from about 50 ppm to about 400 ppm; and 
 water. 
 
     
     
       2. The ink composition as defined in  claim 1  wherein:
 the hydroxylated co-solvent is selected from the group consisting of 2-methyl-1,3-propanediol, 2-hydroxyethyl-2-pyrrolidinone, 2-ethyl-2-hydroxymethyl-1,3-propanediol, di-(2-hydroxyethyl)-5, 5-dimethylhydantoin, glycerol, diethylene glycol, triethylene glycol, tripropylene glycol, tetraethylene glycol, dipropyleneglycol, 3-methyl-1,3-butanediol, 3-methyl-1,5-pentanediol, 1-(2-hydroxyethyl)-2-imidazolidinone, 1,6-hexanediol, 1,5-pentanediol, and combinations thereof; and 
 the non-hydroxylated co-solvent is selected from the group consisting of 2-pyrrolidinone, sulfolane, diethyleneglycol dimethyl ether, and combinations thereof. 
 
     
     
       3. The ink composition as defined in  claim 2 , excluding:
 any other co-solvents; and 
 acids chosen from stearic acid, elaidic acid, linolenic acid, saturated fatty acids having a carbon chain of fewer than 11 carbons, and saturated fatty acids having a carbon chain of more than 13 carbons. 
 
     
     
       4. The ink composition as defined in  claim 1  wherein:
 the isocyanate is selected from the group consisting of 1,6-hexamethylene diisocyanate (HDI), isophorone diisocyanate (IPDI), trimethylhexamethylene diisocyanate (TMDI), 2,4-toluene diisocyanate (2,4-TDI), 2,6-toluene diisocyanate (2,6-TDI), 4,4′-diphenylmethane diisocyanate (MDI), 4,4-dicyclohexylmethane diisocyanate (H 12 MDI), 3,3′-dimethyl-4,4′-biphenyl diisocyanate (TODI), dodecane diisocyanate (C 12 DI), 1,5-naphthalene diisocyanate (NDI), m-tetramethylene xylylene diisocyanate (TMXDI), 1,4-benzene diisocyanate, trans-cyclohexane-1,4-diisocyanate, and 4,6-xylyene diisocyanate; 
 the first diol is selected from the group consisting of dimethylol acetic acid, 2,2′-dimethylol butanoic acid, 2,2′-dimethylol propionic acid (DMPA), and 2,2′-dimethylol butyric acid; and 
 the second diol is selected from the group consisting of 1,2-propanediol, 1,3-propanediol, ethylene glycol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,2-hexanediol, neopentyl glycol, 2-methyl-1,3-propanediol, 3-methyl-1,5-pentane diol, and combinations thereof. 
 
     
     
       5. The ink composition as defined in  claim 4  wherein the at least three diols include one diol from the group of the first diol and two diols from the group of the second diol. 
     
     
       6. The ink composition as defined in  claim 4  wherein the at least three diols further includes one diol from the group of the first diol, one diol from the group of the second diol, and a third diol i) having a formula OH—R—OH, wherein R is selected from the group consisting of a polyether, a polyester, a polycarbonate, a polycarbonate-co-polyester, and an acrylic, or ii) having a formula OH—R 4 —OH, wherein R 4  is a C 1 -C 7  alkyl, or a C 6 -C 40  aryl, or a C 9 -C 40  aryl substituted by C 1 -C 10  alkyl. 
     
     
       7. The ink composition as defined in  claim 4  wherein a number average molecular weight of the polyurethane copolymer binder ranges from about 3500 to about 10,000. 
     
     
       8. The ink composition as defined in  claim 1  wherein:
 the hydroxylated co-solvent is present in an amount ranging from about 9 wt % to about 14.5 wt % of the total wt % of the ink composition; 
 the non-hydroxylated co-solvent is present in an amount ranging from about 9 wt % to about 10.5 wt % of the total wt % of the ink composition; and 
 the weight percentage of each of the hydroxylated co-solvent and the non-hydroxylated co-solvent is selected to satisfy the weight percent ratio. 
 
     
     
       9. The ink composition as defined in  claim 1  wherein the hydroxylated co-solvent is 2-methyl-1,3-propanediol, and the non-hydroxylated co-solvent is 2-pyrrolidinone, and the weight percent ratio is about 50:50. 
     
     
       10. The ink composition as defined in  claim 1  wherein the hydroxylated co-solvent is 2-hydroxyethyl-2-pyrrolidinone, and the non-hydroxylated co-solvent includes a combination of 2-pyrollidinone and sulfolane, and the weight percent ratio is about 56:44. 
     
     
       11. The ink composition as defined in  claim 1  wherein:
 the colorant is chosen from self-dispersed pigments, polymer dispersed pigments, dyes, and combinations thereof; 
 the colorant is present in an amount ranging from about 2 wt % to about 6.5 wt % of a total wt % of the ink composition; 
 a polyurethane copolymer binder is present in an amount ranging from about 1.0 wt % to about 3.0 wt % of the total wt % of the ink composition; and 
 the acid is present in an amount ranging from about 0.03 wt % to about 1.0 wt %. 
 
     
     
       12. A print cartridge, comprising:
 a fluid reservoir; 
 a fluid ejector in fluid communication with the fluid reservoir; 
 a nozzle in fluid communication with the fluid ejector; 
 an ink composition present in the fluid reservoir, the ink composition including:
 a colorant present in an amount ranging from about 2.0 wt % to about 6.0 wt % of a total wt % of the ink composition; 
 a hydroxylated co-solvent; 
 a non-hydroxylated co-solvent, wherein a weight percent ratio of the hydroxylated co-solvent to the non-hydroxylated co-solvent in the ink composition ranges from 46:54 to about 62:38; 
 an acid selected from the group consisting of oleic acid, linoleic acid, undecanoic acid, dodecanoic acid, tridecanoic acid, and combinations thereof; 
 a polyurethane copolymer binder formed from the polymerization of a diisocyanate and at least three diols including a first diol containing a hydrophilic stabilizing group, and a second diol having less than 8 atoms in a backbone chain between two hydroxyl groups, wherein a mole percentage of the second diol is at least 30% of a total mole percentage of diol monomers in the polyurethane copolymer binder, and wherein an acid number of the polyurethane copolymer binder ranges from 50 to 75, the polyurethane copolymer binder present in an amount ranging from about 1.0 wt % to about 3.0 wt % of the total wt % of the ink composition; 
 lithium present in an amount ranging from about 50 ppm to about 400 ppm; and 
 water; and 
 
 an anti-evaporative layer present at an interface between air and the ink composition in an orifice of the nozzle, the anti-evaporative layer formed during uncapped non-use, thereby reducing evaporation of the water from the ink composition. 
 
     
     
       13. The print cartridge as defined in  claim 12  wherein:
 the hydroxylated co-solvent is selected from the group consisting of 2-methyl-1,3-propanediol, 2-hydroxyethyl-2-pyrrolidinone, 2-ethyl-2-hydroxymethyl-1,3-propanediol, di-(2-hydroxyethyl)-5, 5-dimethylhydantoin, glycerol, diethylene glycol, triethylene glycol, tripropylene glycol, tetraethylene glycol, dipropyleneglycol, 3-methyl-1,3-butanediol, 3-methyl-1,5-pentanediol, 1-(2-hydroxyethyl)-2-imidazolidinone, 1,6-hexanediol, 1,5-pentanediol, and combinations thereof; and 
 the non-hydroxylated co-solvent is selected from the group consisting of 2-pyrrolidinone, sulfolane, diethyleneglycol dimethyl ether, and combinations thereof. 
 
     
     
       14. The print cartridge as defined in  claim 12  wherein:
 the isocyanate is selected from the group consisting of 1,6-hexamethylene diisocyanate (HDI), isophorone diisocyanate (IPDI), trimethylhexamethylene diisocyanate (TMDI), 2,4-toluene diisocyanate (2,4-TDI), 2,6-toluene diisocyanate (2,6-TDI), 4,4′-diphenylmethane diisocyanate (MDI), 4,4-dicyclohexylmethane diisocyanate (H 12 MDI), 3,3′-dimethyl-4,4′-biphenyl diisocyanate (TODI), dodecane diisocyanate (C 12 DI), 1,5-naphthalene diisocyanate (NDI), m-tetramethylene xylylene diisocyanate (TMXDI), 1,4-benzene diisocyanate, trans-cyclohexane-1,4-diisocyanate, and 4,6-xylyene diisocyanate; 
 the first diol is selected from the group consisting of dimethylol acetic acid, 2,2′-dimethylol butanoic acid, 2,2′-dimethylol propionic acid (DMPA), and 2,2′-dimethylol butyric acid; 
 the second diol is selected from the group consisting of 1,2-propanediol, 1,3-propanediol, ethylene glycol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,2-hexanediol, neopentyl glycol, 2-methyl-1,3-propanediol, 3-methyl-1,5-pentane diol, and combinations thereof; and 
 the at least three diols further include a third diol having a formula OH—R—OH, where R is selected from the group consisting of a polyether, a polyester, a polycarbonate, a polycarbonate-co-polyester, and an acrylic. 
 
     
     
       15. A method for improving capped recovery performance of an ink composition having a high solids content, the method comprising:
 selecting a polyurethane copolymer binder formed from the polymerization of a diisocyanate and at least three diols including a first diol containing a hydrophilic stabilizing group, and a second diol having less than 8 atoms in a backbone chain between two hydroxyl groups, wherein a mole percentage of the second diol is at least 30% of a total mole percentage of diol monomers in the polyurethane copolymer binder, and wherein an acid number of the polyurethane copolymer binder ranges from 50 to 75; 
 selecting a hydroxylated co-solvent; 
 selecting a non-hydroxylated co-solvent; and 
 incorporating a weight percent ratio of the hydroxylated co-solvent to the non-hydroxylated co-solvent into a mixture, the weight percent ratio of the hydroxylated co-solvent to the non-hydroxylated co-solvent ranging from about 46:54 to about 62:38, and the mixture including:
 from about 0.03 wt % to about 1.0 wt % of an acid selected from the group consisting of oleic acid, linoleic acid, undecanoic acid, dodecanoic acid, tridecanoic acid, and combinations thereof; 
 from about 2.0 wt % to about 6.5 wt % of a colorant; 
 from about 1.0 wt % to about 3.0 wt % of the polyurethane copolymer binder; 
 from about 4.5 wt % to about 9.0 wt % of a combination of the colorant and the polyurethane copolymer binder; 
 from about 50 ppm to about 400 ppm of lithium; and 
 a balance of water.